A recent vulnerability report has surfaced about an XML External Entity (XXE) vulnerability, deemed as CVE-2024-40075, affecting Laravel v11.x. An XXE attack is a type of attack against an application that parses XML input. It can potentially allow malicious actors to exploit the application's XML parser to access sensitive information or invoke remote services. In this post, we will discuss the technical details of this vulnerability in Laravel, showing code snippets and providing original references. We will also outline the steps to reproduce this exploit and share the official patch launched to mitigate this security issue.

Vulnerability Details

A researcher discovered a security vulnerability within Laravel v11.x's XML parser. The vulnerability appears when XML data is uploaded by unsuspecting users, enabling attackers to exploit the XML parser. Attackers can perform various actions, such as reading local files and exfiltrating sensitive data from the server, by injecting malicious XML content. This security flaw has been designated with the identifier CVE-2024-40075.

In Laravel v11.x, the vulnerable code can be found within the XML parser component, where it fails to disable external entities while parsing the XML content. The following code snippet shows the vulnerability in action:

// Vulnerable code in Laravel v11.x
$parser = xml_parser_create();
xml_parse_into_struct($parser, $input_data, $values, $index);
xml_parser_free($parser);

Exploit Details

As previously mentioned, attackers can potentially access sensitive data through this vulnerability. To demonstrate this, we will use an example payload as shown in the following XML code:

<?xml version="1." encoding="UTF-8"?>
<!DOCTYPE exploit [
 <!ENTITY xxe SYSTEM "file:///etc/passwd">
]>
<content>
 <data>&xxe;</data>
</content>

By uploading the XML content above, an attacker could potentially access the /etc/passwd file, which contains sensitive data such as user account details.

If you wish to delve deeper into the exploit's inner workings, you can refer to the following sources:

- Original vulnerability report and discussion
- Exploit database entry

Mitigation Steps

The Laravel development team has been informed about the vulnerability and promptly released a patch for the affected versions. The provided patch disables the external entities during the XML parsing process to prevent potential XXE attacks.

Install the latest patch following the steps mentioned in the official release notes

- Laravel official patch release notes

The patched code in Laravel can be seen below

// Patched code in Laravel v11.x
$parser = xml_parser_create();
// Disable external entity loading
xml_parser_set_option($parser, XML_OPTION_SKIP_WHITE, 1);
xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, );
xml_parser_set_option($parser, XML_OPTION_TARGET_ENCODING, "UTF-8");
// Perform the XML parsing
xml_parse_into_struct($parser, $input_data, $values, $index);
xml_parser_free($parser);

Conclusion

The CVE-2024-40075 XXE vulnerability in Laravel v11.x is a critical issue that needs to be addressed immediately. It is advised to update your Laravel installation to the latest patch as soon as possible, ensuring the security of your server and preventing potential malicious exploits. Stay updated on the latest security news and keep your systems patched to reduce the risk posed by vulnerabilities.

Timeline

Published on: 07/22/2024 19:15:02 UTC
Last modified on: 12/02/2024 18:15:10 UTC